I've played around with Dojo in the past but my primary Javascript framework has always been either Prototype or MooTools. In both cases they have some really useful functions built into them. One of the best in MooTools is the $ function which has been extended to allow you to select pretty much anything in your HTML without having to do lots of nested loops. So for example if I have some HTML like this (because, of course, we shouldn't use non-unique ids on HTML elements, should we):